The study – published in Food Research International – offers insights into the optimal processing conditions for the production of colloidal dispersions with lemon oil. The research team, led by Professor Julian McClements from the University of Massachusetts , USA, studied the influence of lemon oil type and surfactant-to-oil ratio on properties of colloidal dispersions – finding that the surfactant-to-oil ratio determines whether emulsions or micro-emulsions are formed. The team added that the type of lemon oil used and storage temperatures have strong influences on the long term stability of these emulsions.
“This study provides useful information for the rational design of food grade colloidal delivery systems for encapsulating flavour oils and other functional lipids for application in foods and beverages,” said the authors,
They added that the study will help industry design and fabricate better colloidal delivery systems that could be suitable for the encapsulation of functional lipophilic components.
McClements and his team explained that there is a need to understand how to formulate effective colloidal delivery systems from food-grade ingredients using economic processing conditions.
“These delivery systems must have suitable physicochemical and sensory properties for the product they are incorporated into (e.g., optical clarity, flavor profile, rheology), and they must remain stable throughout the shelf-life of the product,” they said.
The most common oil phases used to prepare soft drinks are flavour oils, such as lemon and orange oils, noted the research team. They added that whilst a number of previous studies have focused on the chemical and physical stability of colloidal systems containing citrus oils, their new study focused on dispersions containing lemon oils.
The research team investigated the influence of lemon oil type (either 1-fold or 4-fold) and concentration on the formation and stability of colloidal dispersions prepared using a food-grade surfactant (Tween 80).
“In particular, we wanted to identify conditions for forming either micro-emulsions or nano-emulsions using these materials,” explained McClements.
The team found the influence of surfactant-to-oil ratio and oil type “had a pronounced influence on the nature of the colloidal dispersions formed, as well as on their storage stability.”
They added that transparent colloidal systems were formed at high surfactant-to-oil ratios, whilst turbid dispersions formed at lower ratios.
“Our results suggest that the solubilisation of lemon oil droplets by surfactant micelles may be a slow process whose rate depends on oil type and storage temperature,” said McClements and his team – noting that solubilisation rates appeared to increase from 4 to 32 °C, and was faster for 4-fold than 1-fold lemon oil.
“We also found that all of the colloidal dispersions formed were unstable to droplet growth when stored at elevated temperatures (55 °C), which can be attributed to accelerated Ostwald ripening and/or coalescence processes,” they added.
McClements said the results “have important implications” for the production of stable emulsions for use in the beverage industry.
Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2011.12.017
“Fabrication and Stability of Colloidal Delivery Systems for Flavor Oils: Effect of Composition and Storage Conditions”
Authors: K. Ziani, Y. Fang, D.J. McClements